Switch with liquid containing tube for keyboard use

ABSTRACT

A switch, particularly adapted for keyboard use, including a resilient deformable tube containing an electrically conductive liquid such as mercury has the tube pinched to part the liquid therein by a pinch wire spring extending generally transversely of the tube and tensioned toward the tube to maintain the switch in a normally open-circuit condition. An actuator spring is provided to press the pinch wire spring away from its tube pinching state and actuate the switch by pressure that may be suitably applied through a push button acting on the actuator spring.

United States Patent Twyford Oct. 29, 1974 SWITCH WITH LIQUID CONTAINING TUBE FOR KEYBOARD USE [75] Inventor: Robert H. Twyford, Great Falls, Va.

[73] Assignee: Mechanical Enterprises Incorporated, Alexandria, Va.

[22] Filed: Apr. 9, 1973 [21] Appl. No.: 349,455

[52] US. Cl. 200/214 [51] Int. Cl. H01h 29/00 [58] Field of Search 200/214, 211, 182, 187

[56] References Cited UNITED STATES PATENTS 3,177,327 4/1965 Weiss 200/211 3,360,625 12/1967 Nickelson 200/211 3,600,537 8/1971 Twyford 200/214 Primary Examiner-I-Ierman Hohauser [57] ABSTRACT A switch, particularly adapted for keyboard use, including a resilient deformable tube containing an electrically conductive liquid such as mercury has the tube pinched to part the liquid therein by a pinch wire spring extending generally transversely of the tube and tensioned toward the tube to maintain the switch in a normally open-circuit condition. An actuator spring is provided to press the pinch wire spring away from its tube pinching state and actuate the switch by pressure that may be suitably applied through a push button acting on the actuator spring.

15 Claims, 11 Drawing Figures PAIENIED 00129 I974 SHEET 3 0F 4 mcmsnnmm 3.845264 I 7 sum uni 4 SWITCH WITH LIQUID CONTAINING TUBE FOR KEYBOARD USE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the field of electric switches and specifically to switches incorporating a resilient deformable tube containing electrically conductive liquid, the tube being pinched to open the switch circuit. Such switches are especially adapted for use in keyboard assemblies as are extensively used in computer and related industries.

2. Description of the Prior Art The relatively recent rapid increase in utilization of computers and related data processing equipment has created many applications for keyboards wherein the keys or push buttons on the keyboard effect actuation of switches integrated into electronic circuits for carrying out the computer or data processing operations. The cost of such keyboards has become a significant factor with the rapid increase for their need in remote terminals, input devices and other peripheral equipment used in computer and data processing applications. Certainly a significant portion of the cost of these keyboards involves the electric switches used in connection with each of the multitude of keys or push buttons required for each keyboard.

Another rapidly growing demand for keyboards with keys or push buttons controlling miniaturized electric switches has even more recently arisen in connection with the development of solid state adding machines and calculators compromising desk top models down to the small pocket size adding machine or calculator. Each of these again requires a miniaturized switch and a key top or push button assembled into a keyboard arrangement for the calculator or adding machine.

Many different electrical switch constructions have been developed for the above-mentioned variety of keyboards, these switches being necessary to generate the requisite electrical signals for computers, data processing equipment, calculators and pocket adding machines, to name a few. The switch designs have ranged from mechanical-electrical proposals through elaborate electronic switching concepts. Considering the critical cost factor in keyboard construction, low initial investment and maintenance free operation with high operational reliability are prime requirements for such switches. In many applications, particularly in the computer and related data processing industries, a satisfactory keyboard switch must provide closure of the electrical circuit, upon depressing the key or push button which actuates the switch, with a bounce free" response. A bounce free circuit closing creates a clear electrical signal wherein a non-erratic rise from one voltage level to another occurs when the switch is closed by depression of the key or push button connected to actuate the switch.

The inability or difficulty in obtaining a bounce free" switch operating characteristic is particularly critical in keyboard switches for computer applications where coded electrical signals must be transmitted rapidly with precise accuracy in sending data from, for example, a remote terminal to a computer location. With many keyboard switches the use of additional components in the form of bounce gates or delay circuits is necessary so that the undesirable, unclean or fluttering closure of the electrical circuit is blanked out and prevented from interfering with proper operation of the solid state circuits controlled by the coded electrical signal data. Obviously the necessity for supplying bounce gates and/or delay circuits adds to the cost of the keyboard and related equipment.

The prior art has generally avoided metal-to-metal contact switches in striving for the ideal of a bounce free switch. Such metal-to-metal contacts are quite prone to produce an unclean fluttering or bouncing closure of the signal in the electrical circuit. Therefore highly refined and elaborate electric switching proposals have been developed and incorporated in keyboard constructions. These can be not only complex but also quite expensive to generate the desired clean coded electrical signal data. In addition they frequently lack the flexibility to make up a keyboard capable of meeting the wide variety of computer and data handling applications.

SUMMARY OF THE INVENTION It is a principal object of this invention to provide a miniaturized manual actuatable electrical switch especially adaptable and usable in generating electrically significant data by use of a multitude of such switches in keyboards designed for computer, data processing, calculators and related fields.

A further primary object of the invention is the provision of an electrical switch capable, upon being actuated, on producing a bounce free" electrical signal characterized by a clean non-erratic change from one voltage level to another for the signal generated upon closure of the switch.

A further object is to provide a key or push button operated switch, particularly suited for the multitude of keyboardapplications now in use, which possesses the advantages of the above object with improved touch or feel in depressing and releasing the switch key or push button for all of the switches on the keyboard while long switch life is achieved.

It is also an object of the instant invention to provide an electric switch for keyboards wherein cost economy is achieved by avoiding the necessity for frequently used bounce gates and delay circuits characteristically required in connection with many heretofore used keyboard switches.

The abovementioned objects, aims and purposes of this invention are substantially met and the shortcomings of the prior art alleviated to a large extent through use of the present invention which includes a switch having a deformable resilient tube containing an electrically conductive liquid such as mercury, with the tube being pinched to part the liquid therein by a pinch wire spring extending generally transversely of the tube and tensioned toward the tube to maintain the switch in a normally open circuit condition. An actuator spring is provided to press the pinch wire spring away fromits tube pinching state and actuate the switch. A key or push button may be appropriately used, acting on the actuator spring, to achieve this switch operation. With this construction there is provided a normally electrically open switch with a simple mechanical construction which is both efficient and inexpensive.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a portion of a printed circuit board having several switches of this invention shown mounted thereon, the board and switches being assembled for incorporation into an electronic keyboard application.

FIG. 2 is a front elevational view of one of the switches shown mounted on the printed circuit board in FIG. 1.

FIG. 3 is a side elevational view of a switch of the invention such as shown mounted on the printed circuit board in FIG. 1.

FIG. 4 is a vertical sectional view taken on line 4-4 of FIG. 3 of the switch of this invention, shown mounted in relation to a section of a printed circuit board.

FIG. 5 is a vertical sectional view taken on line 5-5 of FIG. 4.

FIG. 6 is a horizontal sectional view taken on line 6-6 of FIG. 4.

FIG. 7 is a bottom plan view of the switch of this invention taken on line 77 of FIG. 4.

FIG. 8 is an exploded view of the switch components excluding the switch housing and push button.

FIG. 9 is an enlarged sectional view taken on line 9-9 of FIG. 7.

FIG. 10 is an enlarged sectional view taken on line Ill-Jill of FIG. 7 and FIG. ll is a partial sectional view similar to FIG. 5 but showing the switch in fully actuated condition with the electrical circuit closed by the mercury within the deformable tube.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Reference may best be made to FIGS. 1, 2 and 3 on the drawings for a showing of the general exterior configuration of the switch 10 of this invention. An illustration of the manner in which several of the switches 10 are to be mounted on a segment of a printed circuit board 12 for assembly into a keyboard application in association with an appropriate enclosing case, connectors, etc., (not shown) for utilization in a keyboard application is shown on FIG. 1.

In FIG. 1, four switches 10 bearing key tops or push buttons displaying, for illustration purposes, the letters A, W, R and F, respectively, are illustrated. It will be understood that the switch, beneath each of the four mounted switches illustrated, is fastened to the segment of the printed circuit board 12 illustrated on FIG. 1. The three broken line outlines 14 on FIG. 1 show locations where three additional switches would be mounted. The holes 15 shown at the diagonal corner of each of the broken line outlines 14 extend through the printed circuit board 12 and accommodate screws which pass upwardly through the board and engage with mounting bores in the housing of each switch 10. The circular tabs 16 exposed where the three switches have not as yet been mounted on board 12 are the metallic contact elements which are engaged by the two contacts of each switch 10 when the switch is fastened by screws to the circuit board 12. The bar elements 17 represent the metallic circuit board strips leading from tabs 16 to the series of connectors 18 suitably lined up for connection along the lower edge of the segment of printed circuit board 12. Of course there are similar circular tabs l6 disposed beneath and connecting with the contacts for each of the four switches 10 which are shown in mounted position on the segment of printed circuit board 12.

Referring for the moment to FIGS. 4 and 5, screws 19 (only one shown in each of these sectional views) are shown which extend up through the printed circuit board 12 and thread into diagonally opposite bores in the housing of each switch It). It will be appreciated that there are two such screws 19 utilized to fasten each switch on the printed circuit board.

In the embodiment of the switch 10 illustrated, it has a generally rectangular body 20 which defines interiorly thereof a cavity 22. An actuator plunger 24 is reciprocably guided 'within the cavity 22 of housing 20. Considering that the components of the switch of this invention may most appropriately be formed from plastic moldings, the guiding action of plunger 24 within cavity 22 of housing 20 is smoothly and effectively promoted by plunger 24 having parallel ridges 25 formed along the length of each of the external four walls of the plunger while the cavity 22 has smooth interior walls. These ridges may best be seen in the exploded view of FIG. 8.

Plunger 24 has a tang 26 at its outer end formed to removably receive and frictionally retain a key top or push button 28. In the embodiment as illustrated, a cruiciform style tang is provided (see FIG. 8) to mate with a similarly formed recess in the key top 28. It will be understood, as well known in the art, that a box or blade style tang may be provided to accommodate an appropriately formed recess in the key top or push button. Although the key tops 28 are desirably removable to be interchangeable so that the assembled switches in a keyboard application may have selected keys displaying the appropriate indicia for the operation to be performed by a particular switch, it will be understood that the key top 28 is pressed down onto the tang 26 with sufficient frictional interference between the tang and recess of the key top such that the key top is fairly firmly retained in position on plunger 24 against easy removal.

The actuator plunger 24 at the end opposite tang 26 has two legs 30 at diagonally opposite corners of the plunger. Each leg 30 carries an outwardly facing hook 32 (See FIGS. 7 and 8). The housing 20 has the walls of its cavity 22 formed with openings at the points where the legs 30 and hooks 32 will reciprocate to provide a ledge 34 for each hook 32 to engage with. The plunger 24, being appropriately molded of plastic, permits the legs 30 to flex inwardly so that in assembly of the plunger 24 within body 20, the hooks 32 are pressed in until the plunger has passed substantially into body 20 whereat the hooks 32 spring out into the openings in the cavity walls of body 20. Thereafter the hooks 32 engage against ledges 34 formed by the cavity openings to prevent plunger 24 from moving out of body 20. Should disassembly be necessary the legs 30 can be flexed inwardly to disengage hooks 32 from ledges 34 permitting plunger 24 to be removed.

By reference to FIGS. 5 and 11, it will be noted that cavity 22 of housing 20 has interior abutments 23 projecting inwardly from opposite walls of the cavity. The

sides of actuator plunger 24 which overlie these abutments 23 have end walls 33. In depressing plunger 24, the end walls 33 of plunger 24 engage abutments 23 within cavity 22 of the housing to act as a downward limit stop for movement of the plunger under pressure applied through the key or push button 28, thus limiting the depressed condition with end walls 33 of the plunger resting on abutments 23 of the housing, as

shown in FIG. 11. This is important in the operation as will be explained.

Disposed within the hollow recess of plunger 24 and within the cavity 22 of body there is located an actuator spring 36 which, as illustrated, is shown in the form of a coil spring having its outer end engaged in a recess 37 formed on the inside of the outer end of plunger 24. The opposite end of actuator spring 36 rests in a circular recess of a spring rider 38. Spring rider 38 has an oblong center opening on the sides of which extend two legs 40 notched at their outer ends to engage with a pinch wire spring 42.

Pinch wire spring 42 preferably is formed of a straight length of spring wire of a metal such as beryllium copper. Although a cylindrical cross section wire is shown to function as the pinch wire spring, it will be understood that other cross sectional shapes may be employed although the cylindrical cross section has some benefit in avoiding sharp edges where the deformable resilient tube is pinched by the wire spring as will be explained.

The housing 20 is provided with recesses 44 and 46 in opposite side walls thereof, the recesses facing inwardly toward the housing cavity 22. The recess 44 provides a ledge 48 on which one end of pinch wire spring 42 rests. As shown in the enlarged sectional detail of FIG. 10, recess 44 has a slot 45 extending from the end of housing 20 through which the end of pinch wire spring 42 is passed to enter recess 44. Also ledge 48 has a slight indentation 49 so that the end of wire spring 42, in resting on ledge 48, will be held against slipping out of recess 44 by lying in indentation 49.

The opposite end of pinch wire spring 42 is disposed in recess 46 and rests on a switch tuning screw 50. Tuning screw 50, which may suitably be an Allan head set screw, is threaded through the end of housing 20 with the end of screw 50 disposed within recess 46 forming the rest for the end of pinch wire spring 42. As will be more apparent from discussion hereinafter, by threading screw 50 in or out of the recess 46, the supported position of the end of wire spring 42 in this recess can be adjusted. This in turn enables adjustment of the degree of tensioning of spring 42 in achieving its function i of pinching the deformable resilient tube. This action enables tuning of the switch so that the extent of travel of the plunger, upon depressing key top 28, at which the circuit changes from open to close may be fairly accurately adjusted.

Within the cavity 22 of housing 20 and at the end of the housing carrying pinch wire spring 42 the housing is provided with a bridge 52. This bridge is yieldably mounted, for a purpose which will become apparent, on four spider supports 54 (FIG. 7) extending from the bridge toward the walls of housing 20 which have the recesses 44 and 46 that retain the ends of pinch wire spring 42 so that bridge 52 is positioned to extend generally transverse to the length of pinch wire spring 42. It also may be noted that the oblong opening of spring rider 38 accommodates the central portion 56 of bridge 52 with the notched legs 40 of the spring rider passing freely on opposite sides of the central portion of the bridge and their notches engaging pinch wire 42.

It may be noted that the center portion 56 of bridge 52 provides a socket 58 opening into cavity 22 and the hollow recess of actuator plunger 24. In some applications a lighted key or push button may be desired for one or more operational modes of a keyboard. By

forming plunger 24 and key top 28 of a transparent or translucent material, socket 58 on the center portion 56 of bridge 52 may conveniently hold a bulb, the electrical leads of which may be suitably connected to apporpriate portions of the printed circuit board 12 or elsewhere. This bulb can be lighted as desired in connection with the functioning operations of the keyboard.

The exposed end surface of bridge 52 has contact retaining pockets 60 adjacent the opposite ends thereof, connected by channels 62 leading inwardly of such pockets to anvil pad 64 on the side of the bridge center portion 56 opposite the location of socket 58.

An elongated deformable resilient tube containing an electrically conductive liquid therein, such as mercury, is mounted to extend through channels 62 across anvil pad 64 with pinch wire spring 42 acting under its normal tension to pinch the tube against the anvil pad 64 of bridge 52 to part the liquid in the tube and maintain a normal open circuit condition for the switch. Tube 70 has the ends thereof closed by contacts 72 which are snapped and held in the contact receiving pockets 60 adjacent the opposite ends of bridge 52.

It will be noted that the contacts 72 are of a size such that they project outwardly a slight distance from each pocket 60 and project from the exposed end of housing 20. As has been noted, the end of the switch housing 20 has bosses 21 aligned with each of the two bores which receive a mounting screw 19 in holding the switch onto the'printed circuit board 12. These circular bosses 21 provide accurate aligning means for mounting the switch and are formed of a diameter such that they enter the holes 15 on the printed circuit board 12 when the switch is initially positioned. As the two mounting screws 19 for each switch are tightened up in switch mounting, the switch is drawn snugly onto the printed circuit board and the slight projection of contacts 72, at the ends of the conductive liquid containing tube 70, is firmly pressed down into the conductive material of the circular tabs 16 on the circuit board. Thus good and effective electrical contact between each contact 72 and the adjoining circuit board conductive tab 16 is assured. The relationship of the projecting contact 72 to the socket 60 on bridge 52 is shown in enlarged section in FIG. 9.

Reference has heretofore been made to the yieldable mounting of bridge 52 relative to the housing by means of the four spider supports 54. This yieldable mounting is also advantageous in relation to the projecting portion of the contacts 72 in that as the switch 10 is drawn snugly down onto the printed circuit board 12 by screws 19 the outward projection of contacts 72 is pressed into the conductive tabs 16 on the board but excessive pressure is avoided and possible destruction of the conducting tab 16 minimized by the slight yieldability of bridge 52 through its plastic mounting spider supports 54. Thus firm pressure of the contact 72 against tab 16 is assured without accessive pressure.

Operation of the switch construction of this invention, as described hereinabove, may best be described with reference to FIGS. 4, 5 and 11. In FIGS. 4 and 5 the switch is in its normal, unactuated, condition with deformable resilient tube 70 pinched between pinch wire spring 42 and the anvil pad 64 on the center portion 56 of bridge 52. As so pinched, the conductive liquid in the tube, such as mercury, is parted and there is an open circuit between the contacts 72 at the opposite ends of this tube. Although spring rider 38 rests through its notched legs 40 on wire spring 42 and limited compression of actuator spring 36 acts to urge the spring rider 38 against wire spring 42, spring 42 is sufficiently tensioned to keep the tube 70 pinched and the open liquid circuit condition. When the plunger 24 is depressed, as by pressing down on key 28, spring 36 is compressed and its pressure increased on spring rider 38. At a point, its increased pressure overcomes the tension of pinch wire spring 42 moving wire spring 32 to the condition or position shown in FIG. 11, at which point the pinched condition of tube 70 has been relieved permitting the conductive liquid to flow together to create a closed circuit condition between contacts 72 at the opposite ends of the tube.

importantly the sole transmitting pressure against wire spring 42 is created and applied through the compression of actuator spring 36. When the plunger 24 is fully depressed, two of its opposite edges 33 rest on ledges 23 of the housing and further depressing force on plunger 24 or key 28 cannot be transmitted to spring 36 or wire spring 42. This assures against excessive deflection of the elongated wire spring 42 beyond the point where, on release of plunger 24, it would not be able to resume its function of pinching tube 70 to open the switch circuit between contacts 72.

Most importantly, recognizing that compression of actuator spring 36, as it is compressed by plunger 24, determines the point at which the tension in wire spring 42 is overcome, the position of switch tuning screw 50 is important. Tuning screw enables the degree or extent of plunger 24 to travel to the point at which the switch closes its circuit to be adjusted for each of a quantity of switches. This is important in keyboards where the touch for the operator and the closing of the circuit for each switch should occur at the same point in travel upon depression of different keys on the keyboard. ln tuning to get good uniformity between a multiplicity of switches, if one switch opens too soon in point of plunger travel, tuning screw 50 may be adjusted into recess 46 to further tension pinch wire spring 42. If another switch travels too far before the switch closes screw 50 of that switch can be backed out to reduce the tension on pinch wire spring 42. Thus, near uniformity in distance of push button travel for switch circuit closure can be achieved among a multitude of switches.

From the description hereinabove it can readily be seen that the switch of the instant invention and a keyboard embodying a multiplicity of such switches solves a number of the problems mentioned as inherent in prior art devices. The switch of this invention includes an extremely uncomplicated mechanism, operable in an efficient manner with a minimum of moving parts.

IT is to be understood that the construction, form and embodiment of the invention herein shown and described are to be taken only as preferred representations of the invention and that various changes and modifications in the arrangement of the components, parts, units, elements, etc. may be resorted to without departing from the disclosure of the invention or the scope of the appended claims.

I claim:

l. A switch comprising:

a housing having a deformable resilient tube with the ends thereof mounted against movement on said housing;

an electrically conductive liquid within said tube;

a pinch wire spring stationarily supported adjacent its ends by said housing to extend generally transversely of and engage said tube, said wire spring being normally tensioned to pinch said tube against a portion of said housing to part said liquid within said tube and thereby maintain an open circuit; and

switch actuator means movable toward said pinch wire spring switch actuator means movable toward said pinch wire spring to engage and deflect said wire spring out of tube pinching engagement to thereby close a circuit through the liquid within said tube.

2. A switch as recited in claim 1 wherein said switch actuator means includes an actuator spring which is compressible to apply force in deflecting said wire spring out of tube pinching engagement.

3. A switch as recited in claim 2 wherein said switch actuator further includes a depressible plunger for compressing said actuator spring and a spring rider between said pinch wire spring and said actuator spring for transmitting said force from said actuator spring to said pinch wire spring.

4. A switch as recited in claim 3 wherein said plunger is provided with a tang which is frictionally engaged in the recess of a manually operable push button to releasably retain said button on said plunger.

5. A switch as recited in claim ll wherein the stationary support adjacent at least one of said pinch wire spring ends includes a switch tuning screw for adjusting the tension of said pinch wire spring.

6. A switch as recited in claim 1 wherein said housing secures contacts at the ends of said resilient tube in contact retaining pockets, said contacts projecting beyond the mounting end of said switch whereby said mounting end presses the projecting contacts toward the mounting surface in fastening said switch on a mounting member.

7. A switch comprising:

a housing having a deformable resilient tube with the ends thereof mounted against movement on said housing, said housing securing contacts at the ends of said resilient tube in contact retaining pockets, said contacts projecting beyond the mounting end of said switch whereby said mounting end presses the projecting contacts toward the mounting surface in fastening said switch on a mounting member, said pockets being disposed in bridge means yieldably supported as a part of said housing so that the projecting contacts yieldably press against the mounting surface;

an electrically conductive liquid within said tube;

a pinch wire spring supported adjacent its ends by said housing to extend generally transversely of and engage said tube, said wire spring being normally tensioned to pinch said tube against a portion of said housing to part said liquid within said tube and thereby maintain an open circuit; and

switch actuator means movable toward said pinch wire spring to engage and move said wire spring out of tube pinching engagement to thereby close a circuit through the liquid within said tube.

3. A switch comprising:

a housing having a deformable resilient tube with the ends thereof mounted against movement within said housing, said resilient tube having contacts at the ends thereof which project beyond the mountacross said cavity, the ends of said tube being supported against movement on said housing;

an electrically conductive liquid within said tube;

a pinch wire spring mounted in the housing cavity exing end of said switch, said contacts being yieldably tending generally transversely of said tube, said supported Said housing to yieldably PreSS wire spring being normally tensioned to pinch said ward the mounting Surface when the Switch is tube against said bridge means of said housing to ten on a ng member; thereby maintain an open circuit; and an electrically Conductive liquid Within Said tube; switch actuator means reciprocably mounted in said a Pinch wire Spring Supported adjacent its ends y cavity to engage and move said spring wire out of said housing to extend generally transversely of and engage said tube, sad wire spring being normally tensioned to pinch said tube against a portion of said housing to part said liquid within said tube and tube pinching engagement to thereby close a circuit through the liquid within said tube, said switch actuator means including an actuator spring within said cavity and a spring rider between said pinch thereby maintain an Open circuit; and wire spring and said actuator spring, said spring swlich aciuator means movable t Pmch rider having notched legs engaging said wire spring wire Sprwg engage and move Spnng on opposite sides of said bridge means. of tube pinching engagement to thereby close a cm 15 A switch comprising. 9 x" i fi the h i Wlthm i a housing reciprocably guiding an actuator plunger c cqmpnsmgi which carries a tang at its outer end removably rea housing having a cavity therein; taming a push button I a deformable {eslhem tube exiendmg gfmerany an actuator spring compressible by said plunger and across said cavity, the ends of said tube being supengaging a Spring rider ported .agamst i P t a bridge mounted on yieldable spider supports adjaan gecm-cauy c-Onducu-ve hquld wlthm S-ald tube cent one end of said housing and having a central Pmch wire Spring -stauonanly mounted m the holisportion over which said spring rider is slideably remg cavity ei-itendm-g gensarany transversely of Said ceived said bridge having contact retaining pocktlibe Sal-d wire Spring bemg riormanyitenslon-ed to ets adjacent the opposite ends thereof connected pmch sald t-ube-agamst a Poitier? of Sald housmg to b channels leadin inward] of said ockets to an thereby maintain an open circuit; and y g y p switch actuator means reciprocably mounted in said cavity to engage and deflect said wire spring out of tube pinching engagement to thereby close a circuit through the liquid within said tube.

10. A switch as recited in claim 9 wherein said switch anvil pad on said central portion;

an elongated deformable resilient tube containing an electrically conductive liquid therewithin and contacts closing the ends of said tube, said contacts being retained in said pockets and said tube lying actuator means includes an actuator spring within said wlthm channels with mid PQ of Said tube cavity which is compressible by a reciprocable plunger etendlhg aCTQSS f l P to apply force in moving said wire spring out of tube a Pinch wlre p h hflvmg F SUPPOTted i hi engagemem cesses on opposite sides of said housing so as to ex- 11. A switch as recited in claim 9 wherein said pinch y transversely of Sald tube, j wire spring is supported at its ends in recesses in the opp h Q y tellsloheq toward Said anvil it ll f th it f id h i pad to pinch said tube against said pad and thereby 12. A switch as recited in claim 11 wherein a switch m'flimaih an p Qlfcuit in the liquid in Said tube; tuning screw supports an end of said pinch wire spring Sald i e Spr ng being engaged by notched legs on for adjusting the tension of said pinch wire spring. said spring rider extending on opposite sides of the 13. A switch as recited in claim 9 wherein said cavity central portion of said bridge whereby depression has bridge means extending thereacross against which of said actuator plunger compresses said actuator said tube is pinched by said wire spring. spring to press on said spring rider and flex said 14. A switch comprising: wire spring out of the pinched condition of said a housing having a cavity therein, said cavity having tube to close the circuit through the liquid in said bridge means extending thereacross; tube. a deformable resilient tube extending generally 

1. A switch comprising: a housing having a deformable resilient tube with the ends thereof mounted against movement on said housing; an electrically conductive liquid within said tube; a pinch wire spring stationarily supported adjacent its ends by said housing to extend generally transversely of and engage said tube, said wire spring being normally tensioned to pinch said tube against a portion of said housing to part said liquid within said tube and thereby maintain an open circuit; and switch actuator means movable toward said pinch wire spring switch actuator means movable toward said pinch wire spring to engage and deflect said wire spring out of tube pinching engagement to thereby close a circuit through the liquid within said tube.
 2. A switch as recited in claim 1 wherein said switch actuator means includes an actuator spring which is compressible to apply force in deflecting said wire spring out of tube pinching engagement.
 3. A switch as recited in claim 2 wherein said switch actuator further includes a depressible plunger for compressing said actuator spring and a spring rider between said pinch wire spring and said actuator spring for transmitting said force from said actuator spring to said pinch wire spring.
 4. A switch as recited in claim 3 wherein said plunger is provided with a tang which is frictionally engaged in the recess of a manually operable push button to releasably retain said button on said plunger.
 5. A switch as recited in claim 1 wherein the stationary support adjacent at least one of said pinch wire spring ends includes a switch tuning screw for adjusting the tension of said pinch wire spring.
 6. A switch as recited in claim 1 wherein said housing secures contacts at the ends of said resilient tube in contact retaining pockets, said contacts projecting beyond the mounting end of said switch whereby said mounting end presses the projecting contacts toward the mounting surface in fastening said switch on a mounting member.
 7. A switch comprising: a housing having a deformable resilient tube with the ends thereof mounted against movement on said housing, said housing securing contacts at the ends of said resilient tube in contact retaining pockets, said contacts projecting beyond the mounting end of said switch whereby said mounting end presses the projecting contacts toward the mounting surface in fastening said switch on a mounting member, said pockets being disposed in bridge means yieldably supported as a part of said housing so that the projecting contacts yieldably press against the mounting surface; an electrically conductive liquid within said tube; a pinch wire spring supported adjacent its ends by said housing to extend generally transversely of and engage said tube, said wire spring being normally tensioned to pinch said tube against a portion of said housing to part said liquid within said tube and thereby maintain an open circuit; and switch actuator means movable toward said pinch wire spring to engage and move said wire spring out of tube pinching engagement to thereby close a circuit through the liquid within said tube.
 8. A switch comprising: a housing having a deformable resilient tube with the ends thereof mounted against movement within said housing, said resilient tube having contacts at the ends thereof which project beyond the mounting end of said switch, said contacts being yieldably supported On said housing to yieldably press toward the mounting surface when the switch is fastened on a mounting member; an electrically conductive liquid within said tube; a pinch wire spring supported adjacent its ends by said housing to extend generally transversely of and engage said tube, sad wire spring being normally tensioned to pinch said tube against a portion of said housing to part said liquid within said tube and thereby maintain an open circuit; and switch actuator means movable toward said pinch wire spring to engage and move said wire spring out of tube pinching engagement to thereby close a circuit through the liquid within said tube.
 9. A switch comprising: a housing having a cavity therein; a deformable resilient tube extending generally across said cavity, the ends of said tube being supported against movement on said housing; an electrically conductive liquid within said tube; a pinch wire spring stationarily mounted in the housing cavity extending generally transversely of said tube, said wire spring being normally tensioned to pinch said tube against a portion of said housing to thereby maintain an open circuit; and switch actuator means reciprocably mounted in said cavity to engage and deflect said wire spring out of tube pinching engagement to thereby close a circuit through the liquid within said tube.
 10. A switch as recited in claim 9 wherein said switch actuator means includes an actuator spring within said cavity which is compressible by a reciprocable plunger to apply force in moving said wire spring out of tube pinching engagement.
 11. A switch as recited in claim 9 wherein said pinch wire spring is supported at its ends in recesses in the opposite walls of the cavity of said housing.
 12. A switch as recited in claim 11 wherein a switch tuning screw supports an end of said pinch wire spring for adjusting the tension of said pinch wire spring.
 13. A switch as recited in claim 9 wherein said cavity has bridge means extending thereacross against which said tube is pinched by said wire spring.
 14. A switch comprising: a housing having a cavity therein, said cavity having bridge means extending thereacross; a deformable resilient tube extending generally across said cavity, the ends of said tube being supported against movement on said housing; an electrically conductive liquid within said tube; a pinch wire spring mounted in the housing cavity extending generally transversely of said tube, said wire spring being normally tensioned to pinch said tube against said bridge means of said housing to thereby maintain an open circuit; and switch actuator means reciprocably mounted in said cavity to engage and move said spring wire out of tube pinching engagement to thereby close a circuit through the liquid within said tube, said switch actuator means including an actuator spring within said cavity and a spring rider between said pinch wire spring and said actuator spring, said spring rider having notched legs engaging said wire spring on opposite sides of said bridge means.
 15. A switch comprising: a housing reciprocably guiding an actuator plunger which carries a tang at its outer end removably retaining a push button; an actuator spring compressible by said plunger and engaging a spring rider; a bridge mounted on yieldable spider supports adjacent one end of said housing and having a central portion over which said spring rider is slideably received, said bridge having contact retaining pockets adjacent the opposite ends thereof connected by channels leading inwardly of said pockets to an anvil pad on said central portion; an elongated deformable resilient tube containing an electrically conductive liquid therewithin and contacts closing the ends of said tube, said contacts being retained in said pockets and said tube lying within said channels with a mid portion of said tube extending across said anvil pad, a pinch wire spring having its ends supported in rEcesses on opposite sides of said housing so as to extend generally transversely of said tube, said wire spring being normally tensioned toward said anvil pad to pinch said tube against said pad and thereby maintain an open circuit in the liquid in said tube; said wire spring being engaged by notched legs on said spring rider extending on opposite sides of the central portion of said bridge whereby depression of said actuator plunger compresses said actuator spring to press on said spring rider and flex said wire spring out of the pinched condition of said tube to close the circuit through the liquid in said tube. 